Prior art electroluminescent apparatus such as signs, segmented displays, dot-matrix displays, moving messages, computer and TV monitors may be comprised of an electroluminescent (EL) device which includes two electrodes and an electroluminescent material or phosphor layer sandwiched between. Typically, the electrodes are permanently attached to the phosphor layer. Over time, the phosphor loses brightness due to aging; however, the electrodes are still functional. It would therefore be beneficial to provide an electroluminescent apparatus which extends the useful life of an electroluminescent device by allowing for replacement of the electroluminescent phosphor layer.
Typical electroluminescent devices also consist of a single disposable unit, which may require that device be discarded once the phosphors have lost some of their brightness. Although the phosphor layer may be one of the least expensive components of the apparatus, the entire device is discarded. It would therefore be beneficial to provide a housing which allows for replacement of the phosphor layer, while allowing the remaining components to be reused.
Electroluminescent phosphor brightness decays based upon the applied voltage, frequency and waveform provided by the electronic circuitry. At a constant initial voltage and frequency, brightness will exponentially decrease with time of operation. Typically, the electroluminescent phosphor is preliminarily aged using a technique referred to as “rapid aging” by aging the devices after fabrication. However, this rapid aging leads to a reduction in brightness and useful lifetime. It would therefore be beneficial to provide a control circuitry which automatically controls the brightness.
It would also be beneficial to have an electroluminescent apparatus which provides an increase in brightness of the electroluminescent sheets and which is reusable, and allows the replacement of the electroluminescent sheet without the necessity to discard the entire device at the end of its useful lifetime.